When power is switched on a system comprising one or more capacitors, these capacitors, until charged have a comparably low ohmic resistance leading to high currents, also referred to as inrush currents. Such capacitors may include discrete capacitors, capacitors in an integrated circuit or parasitic capacitances. A similar effect may occur for example when switching on a light bulb. While a filament of the light bulb is still cold, it has a very low resistance leading to a high inrush current. Only when the filament is heated sufficiently by a supplied current, the resistance increases. Various approaches have been used to deal with this problem and to limit the inrush current, for example to prevent overheating and possible damage of components and devices used. However, conventional approaches have various drawbacks. For example, in some approaches a current limitation is used where a single MOSFET (metal oxide semiconductor field effect transistor) used as power switch is operated in a saturation region. Such an approach may be difficult with more recent MOSFET technologies due to various properties of the MOSFETs. In other approaches, a resistor is used to limit the current. In such an approach, usually a further switch is needed to bypass the resistor in normal operation. In some implementations, an area needed for such a resistor and costs associated therewith may be comparatively high.
Various approaches regarding limitation of such an inrush current are discussed in U.S. Pat. Nos. 6,225,797 B1; 7,787,271 B2; EP 0 569 883 A2; EP 2 398 146 A2 or WO 00/21176 A1.
It is therefore an object to provide improved possibilities for supplying loads having an inrush-current behavior as discussed above, for example for charging a capacitor or supplying a light bulb.